Poppy Akter, from the same factory, said: “I have been scolded with very bad language, slapped, pulled by the hair, made to stand on the table and threatened to be fired and sent to jail.”

Fazlul Huq, from an Adidas supplier, said managers swore at staff using “obscene” language. “The supervisors and line-chiefs do very bad things to the girls,” she said.

Many of the other women said managers made them remove the dupatta (scarf) they used to cover their breasts. Most of the workers are women. Many of them despair of ever fighting their way out of poverty to live a normal family life.

Adidas is the official outfitter of the London 2012 Olympics, supplying UK team uniforms designed by Stella McCartney and the uniforms for the 70,000 volunteers who will be helping to run the Games. It also sponsors many of the high-profile athletes expected to compete at the Games, including David Beckham and Jessica Ennis.

Adidas hopes to sell £100 million ($192 million) of Olympic-themed sportswear. Nike currently has about 18 per cent of the £4 billion British market, just ahead of Adidas. Nike is reported to have sponsored about 25 national teams, including those of the US, China and Germany. Puma sponsors defending 100m and 200m champion Usain Bolt, along with several national teams.

Greg Muttitt, the campaigns and policy director at War on Want, said: “Companies like Adidas, Nike and Puma make huge profits from this abuse, while soiling the Olympic flag in which they wrap themselves. Let’s focus on what’s great about the Olympics and end the corporate free-for-all.”

Investigators found that at the two factories supplying Adidas, the basic salary of the lowest-paid workers was on average 72p a day. The minimum wage is equivalent to 94p a day.

Factories supplying all three companies broke the law on overtime. A Nike spokeswoman said: “Nike takes working conditions in our contract factories very seriously. All Nike suppliers must adhere to our code of conduct. We are investigating the allegations.”

Adidas said: “All of our suppliers in Bangladesh are subject to regular audits, including monitoring visits by a women’s NGO, which interviews workers and examines workplace conditions. We also run a telephone hotline to address worker complaints.”

The company said it had identified “critical issues” at one of the factories last year relating to working hours and wages, which resulted in enforcement action. It said the underpayment of minimum wages had been resolved by the factory. It said it was “deeply concerned about reports of harassment or physical abuse of workers” and would immediately launch an investigation.

Puma said it had found evidence of illegal overtime in one of its supplier factories named in the War on Want report, but said the factory had offered assurances that it would tackle the problem. It said it paid the legal minimum wage.

War on Want is urging people who want to support its campaign to email STOP to olympics@waronwant.org.